This invention relates to a blow molding method and a blow molding apparatus which are capable of achieving blow molding efficiently with a relatively few molds, cooling blow molding products efficiently in a short period of time, performing a series of blow molding processes including takeout of products and attaching of labels to the molds efficiently, and coping with a variety of production styles ranging from a small scale production to a large scale production.
Blow molding is a popular method for forming hollow containers. In blow molding, a parison extruded from a die head is received by an opened pair of mold pieces of a split mold, the split mold is closed and air is blown into the parison and then the split mold is opened to take out a product.
Blow molding apparatuses for performing such blow molding are generally classified by a manner of moving of split molds into a rotary type blow molding apparatus in which split molds are moved in a circle and a shuttle type blow molding apparatus in which split molds are reciprocated linearly.
In the rotary type blow molding apparatus, split molds mounted on an annular rail are moved in a circle and are opened and closed continuously, whereby blow molding and delivery of a product are completed in one cycle of movement of each split mold on the annular rail.
In the shuttle type blow molding apparatus, two pairs of split molds which reciprocate linearly are provided and these split molds are alternately reciprocated for receiving parisons and for blow molding the parisons.
Accordingly, in a case where a single type of hollow container should be produced in a large scale, the rotary type blow molding apparatus may preferably be employed so that blow molding will be performed efficiently by using a relatively large number, for example 12 to 14, of split molds arranged in a circle.
The shuttle type blow molding apparatus which performs blow molding by alternate reciprocating movement of the two split molds is limited in its blow molding capacity even if the speed of reciprocating movement is increased and, for this reason, is not suitable for a large scale production but suitable for a small scale production.
In a case where a small scale production of various types of products is required for coping with requirement for various types of hollow containers, the rotary type blow molding apparatus has the disadvantage that split molds which are mounted on the apparatus in a set of 12 to 14 split molds must be changed and this takes much time and further it is costly to produce so many split molds.
The shuttle type blow molding apparatus is suitable for such small scale production of various types of products in that change of split molds does not take much time because the number of split molds used is small and the manufacturing cost of split molds is relatively small. The shuttle type blow molding apparatus, however, is limited in its blow molding capacity in a case where a large scale production is required.
There are many cases where a label must be attached to a product which has been produced by blow molding and, in such cases, a label is generally attached to a product simultaneously with performing of blow molding. For this purpose, a product is taken out of an opened split mold after blow molding by means of a product takeout robot and thereafter a label is attached to the split mold by means of a label attaching robot. Thus, two different robots are required and, since it takes a long cycle time for operating these robots, an efficient blow molding cannot be achieved.
Further, the cycle time of the operation of the robots is determined by speed of cooling in blow molding. Cooling of the inside of a parison is difficult when a label is attached so that improvement in efficiency in cooling is desired for.
Furthermore, a product taken out of a split mold generally has flash and, therefore, a step using a device for removing flash from the product becomes necessary for obtaining a final product by blow molding.
It is, therefore, an object of the invention to provide a blow molding method and a blow molding apparatus which are capable of performing blow molding efficiently with a relatively few split molds.
It is another object of the invention to provide a blow molding method and a blow molding apparatus which are capable of cooling a product efficiently in a short period of time.
It is another object of the invention to provide a blow molding method and a blow molding apparatus which are capable of efficiently performing a series of blow molding operations including taking out of a product and attaching of a label to a split mold.
It is still another object of the invention to provide a blow molding method and a blow molding apparatus which are capable of performing blow molding efficiently both in a small scale production and in a large scale production.
For achieving the above described objects of the invention, there is provided a blow molding method comprising steps of moving a split mold to a parison receiving position where a parison is supplied and receiving the parison, closing the split mold, performing blow molding at a blow molding position, and opening the split mold at a product discharging position and thereby discharging a product, said method further comprising steps of:
sequentially reciprocating each split mold in trains of split molds provided opposed to each other across the parison receiving position to and from a position opposed to the parison receiving position; and
sequentially reciprocating the split mold between the position where the split mold is opposed to the parison receiving position and the parison receiving position for performing blow molding.
According to the invention, by combination of the two reciprocating movements, namely the reciprocating movement of the trains of split molds to and from the position opposed to the parison receiving position and the reciprocating movement of the split molds between the position opposed to the parison receiving position and the parison receiving position, blow molding can be performed efficiently with a smaller number of split molds and replacement of split molds can be finished in a shorter period of time than the blow molding using the rotary type blow molding apparatus.
In one aspect of the invention, the direction of reciprocation of each split mold in the trains of the split molds to and from the position opposed to the parison receiving position crosses, at right angle, the direction of reciprocation of the split mold between the position opposed to the parison receiving position and the parison receiving position.
According to this aspect of the invention, blow molding can be performed simply and efficiently by the two reciprocating movements crossing at right angle such as x-y directions.
In one aspect of the invention, a plurality of parisons are supplied simultaneously at the parison receiving position to each split mold which are adapted to receive the plurality of parisons.
According to this aspect of the invention, the blow molding capacity is improved by the multiple supply of parisons and the multiple cavities of the split mold.
In another aspect of the invention, there is provided a blow molding method comprising steps of performing blow molding by supplying a parsion in a split mold and closing the split mold and thereafter discharging a product by opening the split mold at a product discharging position, said method further comprising steps of:
reciprocating a pair of arms capable of being opened and closed relative to each other between the product discharging position, a first delivery position and a second delivery position provided at an equal interval downstream of the product discharging position in the direction of delivering the product, said pair of arms having length corresponding to the interval between the first delivery position and the second delivery position and a label supplying section being provided in correspondence to the first delivery position; and
opening and closing the pair of arms sequentially among a product holding and releasing state in which the arms are closed for holding the product and opened for releasing the product, a label takeout state in which the arms are opened for taking out a label from the label supplying section, a label attaching state in which the taken out label is attached to the split mold and an intermediate state in which the arms enter between the opened split mold and the product and thereby performing delivery of the product and taking out and attaching of the label.
According to this aspect of the invention, takeout of the product and attaching of a label to the split mold can be achieved by opening and closing and reciprocating movement of the pair of arms and, therefore, blow molding can be achieved efficiently with a smaller number of split molds than in the blow molding using the rotary type blow molding apparatus. Moreover, the cycle time required for taking out of the product and attaching of a label can be shortened.
In another aspect of the invention, the method further comprises a step of removing flash in a bottom portion of the discharged product at the first delivery position so as to enable the product to be placed in position.
According to this aspect of the invention, the product can be placed at the first delivery position with its bottom portion down at the first delivery position.
In another aspect of the invention, the method further comprises a step of removing flash about a side portion of the discharged product at the second delivery position.
According to this aspect of the invention, flash can be completely removed from the product during the process between taking out of the product from the split mold and delivering out of the product.
In another aspect of the invention, the method further comprises a step of receiving the product at the second delivery position, changing direction of the product and lowering the product for a next step.
According to this aspect of the invention, the product is confined to a desired state and transferred in this state to a next step and, therefore, processing in the next step can be facilitated.
In another aspect of the invention, there is provided a blow molding apparatus of a type in which a split mold is moved to a parison receiving position where a parison is supplied, is closed for performing blow molding at a blow molding position and is opened at a product discharging position for discharging a product, said apparatus comprising:
trains of split molds provided opposed to each other across the parison receiving position;
a first reciprocating section which sequentially reciprocates each split in the trains of the split molds to and from a position opposed to the parison receiving position;
a second reciprocating section which sequentially reciprocates each split mold of the trains of the split molds to and from the parison receiving position in a direction crossing the direction of movement of the first reciprocating section; and
a reciprocation control section which controls the first reciprocating section and the second reciprocating section for performing blow molding by reciprocating each split mold to and from the parison receiving position and to and from the product discharging position.
According to this aspect of the invention, by combination of the two reciprocating movements, blow molding can be performed efficiently with a smaller number of split molds and replacement of split molds can be finished in a shorter period of time than the blow molding using the rotary type blow molding apparatus.
In another aspect of the invention, the direction of movement of the first reciprocating section crosses the direction of movement of the second reciprocating section at right angle.
According to this aspect of the invention, blow molding can be performed simply and efficiently by the two reciprocating movements crossing at right angle such as x-y directions.
In another aspect of the invention, the first reciprocating section and the second reciprocating section each comprise a moving table which is constructed in the form of a box made by welding plates.
According to this aspect of the invention, the moving tables are made light-weight so that load in reciprocating movements is reduced to thereby enhance the efficiency of the blow molding.
In another aspect of the invention, there is provided a blow molding apparatus of a type in which an extruded parison is held by a split mold and the parison is formed after a configuration of a cavity of the split mold by blowing compressed gas in the parison, said apparatus comprising:
a blow nozzle communicating with the inside space of the parison held by the split mold; and
a blowing and cooling pipe provided in the central portion of the blow nozzle slidably relative to the blow nozzle for blowing compressed gas into the parison and being inserted into a swollen intermediate product for cooling it with the compressed gas.
The intermediate product herein means a swollen parison held in the split mold during blow molding in contrast to a parison in the state of tubular molten resin which has been extruded from a die head.
According to this aspect of the invention, by inserting the blowing and cooling pipe to the inside of the intermediate product, portions where cooling is particularly necessary such as a pinched off portion of a parison (thick portion in a product) and a portion inside of a label can be cooled concentrically. Thus, the cooling efficiency is improved and a product can be taken out in a short period of time whereby the efficiency of blow molding is improved.
In another aspect of the invention, the apparatus further comprises a first reciprocating unit which causes the blow nozzle to communicte with the inside space of the split mold and a second reciprocating unit which inserts the blowing land cooling pipe into the swollen intermediate product, a reciprocating plane of the first reciprocating unit being offset from a reciprocating plane of the second reciprocating unit.
According to this aspect of the invention, addition of the two reciprocating strokes is prevented whereby a compact design of the apparatus can be realized without requiring a bulky apparatus.
In another aspect of the invention, the blowing and cooling pipe comprises a nozzle member which blows compressed gas against a portion of the parison to be cooled.
According to this aspect of the invention, compressed gas can be blown further efficiently to portions where cooling is particularly necessary such as a pinched-off portion and an inside portion of a label of the parison whereby the cooling efficiency can be improved.
In another aspect of the invention, the apparatus further comprises a moving table which is reciprocated by the first reciprocating unit, said moving table being constructed in the form of a box made by welding plates.
According to this aspect of the invention, the apparatus can be made light-weight while supporting load such as moment acting on the moving table.
In another aspect of the invention, there is provided a blow molding apparatus of a type in which a parison is supplied in a split mold, the split mold is closed for blow molding and opened for discharging a product at a product discharging position, said apparatus comprising:
a pair of arms capable of being opened and closed relative to each other and reciprocating between the product discharging position, a first delivery position and a second delivery position provided respectively at an equal interval downstream of the product discharging position in the direction of delivering the product, said pair of arms having length corresponding to the interval between the first delivery position and the second delivery position and comprising product holding sections provided between the pair of arms in end portions of the arm and a label holding section provided in the outside of end portions of the arms on the upstream side in the direction of delivering the product;
a label supplying section provided at the first delivery position; and
an arm opening and closing section provided in the pair of arms for opening and closing the pair of arms sequentially among a product holding and releasing state in which the arms are closed for holding the product and opened for releasing the product, a label takeout state in which the arms are opened for taking out a label from the label supplying section, a label attaching state in which the taken out label is attached to the split mold and an intermediate state in which the arms enter between the opened split mold and the product and thereby performing delivery of the product and taking out and attaching of the label.
According to this aspect of the invention, by reciprocating the pair of arms between the three positions of the product discharging position, the first delivery position and the second delivery position, with the pair of arms being present at two of the three positions at a time and opening and closing the pair of arms at the respective opening and closing states, delivery of the product and taking out and attaching of the label can be performed and, therefore, blow molding can be achieved efficiently with a smaller number of split molds than in the blow molding using the rotary type blow molding apparatus and, moreover, the cycle time required for taking out the product and attaching of the label can be shortened.
In another aspect of the invention, the arm opening and closing section comprises:
a cam groove formed in each of the arms;
a pivoting arm having a roller at each end thereof, said roller being engaged in one of the cam grooves of the pair of arms; and
drive means for driving and pivoting the pivoting arm.
According to this aspect of the invention, opening and closing of the pair of arms can be controlled in a simple and accurate manner by controlling the pivoting angle of the pivoting arm.
In another aspect of the invention, said product holding sections of the pair of arms are detachable in correspondence to configuration of the product.
According to this aspect of the invention, the product holding sections can be replaced easily when the shape of the product has been changed.
In another aspect of the invention, the product holding section on the downstream side in the direction of delivering the product is constructed in a shape capable of removing flash in an upper side portion of the product in a state in which the product is held by the arms.
According to this aspect of the invention, flash can be removed while the product is held by the product holding section of the pair of arms so that flash can be removed accurately and completely.
In another aspect of the invention, the label supplying section is adjustable in its vertical position and a pivoted position about a horizontal pivot axis in accordance with a state of mounting of a label on the split mold.
According to this aspect of the invention, a label can be attached to the split mold in a desired state of attachment (e.g., position and angle of attachment).
In another aspect of the invention, the apparatus further comprises a bottom portion flash removing section which removes flash in a bottom portion of the discharged product at the first delivery position so as to enable the product to be placed in position.
According to this aspect of the invention, the product can be placed at the first delivery position with its bottom portion down at the first delivery position.
In another aspect of the invention, said bottom portion flash removing section comprises a pair of push rods which are provided on both sides of a central axis of the product and are moved to project toward the central axis of the product.
According to this aspect of the invention, by pinching flash on both sides with the pair of push rods and projecting the push rods, the flash can be twisted and removed. Thus, flash can be removed in a simple manner.
In another aspect of the invention, the apparatus further comprises a flash removing section which removes flash about an upper side portion of the discharged product at the second delivery position.
According to this aspect of the invention, flash can be removed completely during the processing between taking out of the product from the split mold and delivering out of the product.
In another aspect of the invention, said flash removing section comprises a screw portion flash removing section which pinches a screw portion at the upper portion of the product and removes flash from the screw portion and a side flash removing section which pinches a side portion of the product and removes flash from the side portion.
According to this aspect of the invention, flash can be completely removed from the product by removing flash in the screw portion and the side portion of the product.
In still another aspect of the invention, the apparatus further comprises a receiving-turning-lowering section which receives the product from the second delivery position, change direction of the product and lowering the product for a next step.
According to this aspect of the invention, the product can be delivered out in a state suitable for a processing in the next step.